#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

void solve() {
    int n, f, a, b;
    cin >> n >> f >> a >> b;
    vector<int> arr(n + 1);
    arr[0] = 0;
    for(int i = 1; i <= n; i++) cin >> arr[i];
    for(int i = 1; i <= n; i++){
        f -= min(arr[i] - arr[i - 1], a + b);
    }   
    cout << (f >= 0 ? "YES" : "NO") << '\n';
}

int main() {
    int t;
    cin >> t;
    while(t--) solve();
    return 0;
}